XML 154 R126.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Estimated discounted future cash flows of total proved reserves (Details 6) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items] |  |  |
Future cash inflows | $ 4,507,000 | $ 3,696,200 | $ 4,188,000
Future production costs | 1,734,800 | 1,536,500 | 1,560,300
Future development costs | 403,000 | 301,600 | 285,300
Future net cash flows before income taxes | 2,369,200 | 1,858,100 | 2,342,400
Future income tax expense | 545,200 | 304,900 | 531,100
Future net cash flows | 1,824,000 | 1,553,200 | 1,811,300
10% annual discount for estimated timing of cash flows | 810,000 | 669,800 | 832,500
Discounted future net cash flows relating to proved oil, NGL and natural gas reserves | $ 1,014,000 | $ 883,400 | $ 978,800

X
- Definition Discounted future net cash flows before income taxes + References No definition available. + Details
Name: | mdu_DiscountedFutureNetCashFlowsBeforeIncomeTaxes
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition This is the amount that is derived from using a discount rate of ten percent a year to reflect the timing of the future net cash flows relating to proved oil and gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 30 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62424-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 31 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62455-109447 + Details
Name: | us-gaap_DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves10PercentAnnualDiscountForEstimatedTimingOfCashFlows
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of estimated future cash inflows from sale of proved oil and gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 30 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62424-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 31 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62455-109447 + Details
Name: | us-gaap_DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureCashInflows
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of estimated future cost to be incurred in developing proved oil and gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 30 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62424-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 31 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62455-109447 + Details
Name: | us-gaap_DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureDevelopmentCosts1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of estimated future income tax expense to be incurred based on the future income less future expense derived from production and sale of proved oil and gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 30 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62424-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 31 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62455-109447 + Details
Name: | us-gaap_DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureIncomeTaxExpense1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of estimated net future cash inflows, after subtracting future development and production costs and future income tax expenses, from sale of proved oil and gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 30 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62424-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 31 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62455-109447 + Details
Name: | us-gaap_DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureNetCashFlows
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of estimated future cost to be incurred in producing proved oil and gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 30 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62424-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 31 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62455-109447 + Details
Name: | us-gaap_DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureProductionCosts1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition This amount is the future net cash flows less the computed discount. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 30 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62424-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 31 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62455-109447 + Details
Name: | us-gaap_DiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReservesStandardizedMeasure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration